So far, I have found two issues with EC:
1. My USB keyboard and USB mouse occasionally do not get enough power when waking from sleep. The only recourse is to do a forced shutdown by holding the power button and then restart. I had thought that my Belkin USB hub was somehow responsible, but that isn't the case. This happens despite the fact that the hub has been disconnected from the computer. Because of the erratic nature of the problem, it's difficult to troubleshoot. According to what I have read, the 10.11.2 beta lists USB issues as one of the things that it contains. I'll see if that update, when released, solves the problem.
2. Since upgrading from Yosemite to EC, my SuperDuper clone will not boot. I started another thread about this but have not had time to fully troubleshoot. My wife's cataract surgery has taken precedence. (She had it done last week and is delighted with the result.)
The only downside is that the operation seems to have killed her sex urge...